1. Field of the Invention
This invention relates to a wheel and tire for an aircraft, and more particularly an improved wheel and tire for an aircraft adapted to be rotated without any driving power before touch-down to reduce friction between a tire and a runway upon touch-down, thereby elongating its life.
2. Description of the Prior Art
The term "wheel and tire" used herein is intended to designate a rotating member in its entirety including a tire and a wheel made of metal centrally located in the tire.
It has been generally said that the life of tires for air-craft, particularly high speed machines is so short that they cannot be used for landing more than several times or at the most twenty times. It is much shorter than that of tires for automobiles. Such a short life results from the friction between the tire and the ground or runway due to the fact that induced rotation of the wheel and tire at touching-down cannot completely match the touch-down speed of the aircraft. It has been therefore proposed to previously rotate tires of an aircraft by wind force or driving power before the touch-down of the aircraft in order to prolong the life of the tires. However, such a proposal has not been practically used because there are various problems in the aerodynamics, flight technique determining the touch-down speed and other factors which are complicated in conjunction with each other and difficult to solve.
In case of a wheel and tire adapted to previously rotate by the wind force before the touch-down, the circumferential velocity of the tire is determined by the "product" of the ratio of induced velocity of wind receiving ledges formed on the tire to the wind velocity (referred to hereinafter "induced rotation rate") and the ratio of the distance between centers of the wind pressure at the wind receiving ledges and the center of the wheel and tire (referred to hereinafter "arm ratio"). However, as the induced rotation rate for determining the circumferential velocity of the wheel and tire varies with factors such as turbulence of the air flow and degree of the turbulent flow and further factors not proportional to air flow velocity, it is very difficult to design a wheel and tire capable of adapting its circumferential velocity to the touch-down speed of an aircraft.